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The non-LTE line formation of neutral carbon in late-type stars
Stockholm University, Faculty of Science, Department of Astronomy. Institutet för solfysik.
2006 (English)In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 458, no 3, 899-914 p.Article in journal (Refereed) Published
Abstract [en]

Aims.We investigate the non-Local Thermodynamic Equilibrium (non-LTE) line formation of neutral carbon in late-type stars in order to remove some of the potential systematic errors in stellar abundance analyses employing C i features.

Methods: .The statistical equilibrium code MULTI was used on a grid of plane-parallel 1D MARCS atmospheric models.

Results: .Within the parameter space explored, the high-excitation C i lines studied are stronger in non-LTE due to the combined effect of line source function drop and increased line opacity due to overpopulation of the lower level for the transitions considered; the relative importance of the two effects depends on the particular combination of T{eff}, log g, [Fe/H] and [C/Fe] and on the analysed C i line. As a consequence, the non-LTE abundance corrections are negative and can be substantially so, for example ˜ -0.4 dex in halo turn-off stars at [Fe/H]˜ -3. The magnitude of the non-LTE corrections is rather insensitive to whether inelastic H collisions are included or not.

Conclusions: .Our results have implications on studies of nucleosynthetic processes and on Galactic chemical evolution models. When applying our calculated corrections to recent observational data, the upturn in [C/O] at low metallicity might still be present (thus apparently still necessitating contributions from massive Pop. III stars for the carbon production), but at a lower level and possibly with a rather shallow trend of ˜ -0.2 dex/dex below [O/H]˜ -1.

Place, publisher, year, edition, pages
2006. Vol. 458, no 3, 899-914 p.
Keyword [en]
ine: formation, stars: abundances, stars:, late-type, Galaxy: abundances, Galaxy: evolution
National Category
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-20164DOI: doi:10.1051/0004-6361:20065763OAI: diva2:186689
Available from: 2008-06-12 Created: 2008-06-12 Last updated: 2011-01-11Bibliographically approved

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